Cooking aids employing mechanical thermal models are known from various documents, e.g. EP 145 953 A2, U.S. Pat. No. 4,085,493 and EP-A 441 432. In this connection, the thermal models are simulated by appropriate materials which reproduce the thermal differential equation of the inner warming of the egg. A thermal sensor, starting a sound provider or indicating the temperature (thermometer), respectively, is then also used for indicating the cooking state. The known starting of a timer above a certain temperature is not precise either, since in this case it is necessary to wait until the water boils before the egg and the cooking aid may be immersed therein, since the influence of heating the water on the cooking state is not simulated correctly. The invention described herein avoids the disadvantages related to the principles of prior art devices.